Mad Deer Disease?

by Dan Richardson


It's a distasteful task, if you're not used to gore and brains. Jim Kujala wears rubber gloves and works a steel hacksaw against a skull. It's the head of a mature buck, severed, on a plywood board, its eyes black and vacant. Not two hours ago, the deer met its fate against the grille of an automobile on Highway 27.


A fresh kill is necessary to get the brain stem in time, Kujala explains. It's part of Washington's new wildlife surveillance program looking for "chronic wasting disease" in area deer and elk.


Kujala's not a biologist, but a volunteer with the Inland Northwest Wildlife Council, a nonprofit Spokane group. Tests for chronic wasting disease (CWD) require fresh brain stems, so Kujala, a 62-year-old Spokane Valley resident, hopped in his pickup and drove to the Wildlife Council's facility on North Market when the road kill call came in one January afternoon.


"There's a handful of reasons," Kujala says when asked why he's sawing open deer brains, "and one of them is concern for the these animals."


Wildlife Council volunteers are the kinds of people who will hunt, yet, like Kujala, get up in the middle of the night to respond to an automobile-injured deer. Animals struck by cars often live, at least for a while, with broken legs, says Kujala. "It's a bad death."


Other road kill volunteers have harvested the deer and strung it on a tall frame by the time Kujala arrives this particular evening. The severed head they've left for Kujala, one of two volunteers in the area trained to get the brainstem sample. (He put on a class to train more, but people got ill watching the process.)


First he skins the head, slicing its fur open and pulling it around the antlers. That exposes a glistening whiteness. Kujala makes a lateral cut, sawing into the skull from the ears to nose. He makes a couple more saw-incisions, wresting with the slimy skull, trying to hold it down while cutting it open.


Pinkish and wrinkled, the brain looks and feels like a fist-sized portion of tofu. At the base of the brain is a smaller mass of brain stem. Placed in a formaldehyde vial, this piece -- the medulla oblongata -- will later tell state Department of Fish and Wildlife Veterinarian Briggs Hall whether the deer suffered from chronic wasting disease.


So far, hunters, game biologists and volunteers have collected about 730 samples for Hall since the fall, plus a few dozen in previous years. No Washington deer or elk have ever tested positive, according to Hall.


The big deal with this particular deer disease is that it is always fatal for the infected animal. There's no evidence people can be infected by CWD, but much about the disease remains mysterious, 34 years after biologists first recognized it in captive deer. The animals wasted away to skin and bones, stood around listlessly, heads down, dripping saliva until they died.


Biologists do know this: CWD is in the same class of diseases as bovine spongiform encephalopathy, or BSE. Laymen know BSE by a different name: mad cow disease.





What makes chronic wasting disease a remote but real concern is the possibility of its infecting people. Scientists say this is unlikely. But the question remains lodged deep, like a sliver they can't quite pull out.


"We know in general these diseases don't jump species lines readily. That doesn't mean it can't happen," says Elizabeth Williams, veterinary science professor at the University of Wyoming. Williams was, in 1978, the researcher who first found evidence of tiny spongelike holes in the brains of CWD victims.


Scientists believe this category of diseases -- those called transmissible spongiform encephalopathies, or TSEs -- occur naturally, but very rarely. They're difficult to transmit between individuals. Most are also apparently specific to one kind of mammal, like scrapie in sheep. Scrapie has been recognized for two centuries but has never been known to infect people, even those in close contact, like shepherds.


Mad cow is unusual and frightening for having apparently jumped the species barrier. Scientists believe mad cow causes a new variant of a human TSE called Creutzfeldt-Jakob. That's why, says Williams and others, "We could never say that it's impossible [CWD] would affect humans."


Some scientists believe mad cow is actually scrapie that jumped the species barrier, because British cattle feed included mashed sheep parts, possibly infected. Regardless of its exact origin, mad cow burst from 12 reported British cases in 1986 to more than 160,000 by the late-1990s. Eventually, feed laws were tightened, but not before destroying the British beef industry and killing about 100 people.


Scientists testing the possibility of cross-species outbreaks of CWD have injected infected cerebral tissue into cows, notes Williams. Several cows later came down with CWD-like disease.


Symptoms can take months, even years, to develop in infected animals. That means research also moves slowly. Cattle penned together with infected deer or elk have remained healthy -- the species barrier appears intact -- but definitive tests will take many more years.





Word of CWD has floated around biology circles for a few decades, and more recently hunters outside Colorado -- where the disease is most concentrated -- have begun asking questions. For the past several years, a number of western states, including Idaho and Washington, have tested suspicious-acting deer.


Hall, the Washington state veterinarian, conducted this targeted testing almost as a hobby, getting maybe a couple dozen tests each year. Mostly they were deer who would wander into yards, acting strange, Hall says. With the advent of mad cow outbreaks, interest in related diseases spiraled. Outdoor magazines began running articles about CWD. Hunters and wildlife officials began asking questions of their own herd's safety. So, in 2001, the Washington Department of Fish and Wildlife (WDFW) received a couple hundred thousand dollars to study several diseases, including CWD, officials say.


"Until this year, we were a little behind the other states in terms of how much we sampled and how much we knew," says Jerry Nelson, WDFW deer and elk section manager.


This autumn, WDFW officials set up checkstands at popular hunting areas and collected a number of samples. So far, none has had any trace of CWD.


Because there's no evidence of risk to humans, Nelson says, he and other biologists consider CWD a game management issue, not a public health problem.


Yet the disease's universal fatality makes it an ongoing concern for wildlife biologists. They've watched it spread from the first recognition in a Colorado research facility full of captive deer in 1967 to wild populations. The disease is concentrated in a small region of northeast Colorado and southeast Wyoming, but some infected animals have turned up in Nebraska, Montana, South Dakota and Saskatchewan, too, mainly in captive herds.


Like other kinds of TSE, CWD appears to be the destructive work not of a virus or bacteria, nor of fungi or protozoa, but of a uniquely active protein. These protein germs are called "proteinaceous infectious particles," or prions.


The germs that appear to cause it are extremely tough and long-lasting. Some have survived, apparently in fecal matter, in plowed-up ground, then infected new animals months later.


CWD isn't raging out of control. Monitoring suggests that perhaps about 5 percent of the deer population in the endemic portion of Colorado has the disease. There are just a few score diagnoses made of newly infected animals each year, according to Williams. The illness is spreading slowly among wild populations, and Williams believes that there's little likelihood wild deer or elk will spread the disease west, over the Rockies into the Northwest. Spreading east is a much likelier scenario, as the animals tend to follow riparian zones -- moving east along the Platte River drainage, into Nebraska, she says.


But animals don't have to be wild to be infected. CWD is a bigger problem in wild game farms, such as the elk farms that dot many Western states and Canadian provinces. (Male elk antlers are sometimes ground into powder and sold for their supposed medicinal value in Asia.) Since the early-1990s, Washington state does not have any such game farms. Idaho does. There are more than 80 throughout the state -- three in Kootenai County -- according to Edward Mitchell, Boise-based spokesman for Idaho Fish and Wildlife (IFW).


The immediate problem with game farms is that animals in close proximity spread disease among each other more easily. Game farms ship animals around the country. This fall, CWD-exposed captive elk from one game herd were shipped around to more than 40 game ranches in Colorado and 15 other states. One of them appears to have been Idaho.





What happened, explains IFW spokesman Mitchell, is that an elk farm near Salmon, in central-east Idaho, imported some animals last spring. Problem was, the elk had come from a farm in Colorado that included animals infected with CWD. When state agriculture officials found out in September, they quarantined the Idaho farm and tested the animals.


"Thirty-seven adult elk were slaughtered. No CWD was found," says Mitchell. "However, it did sharpen everybody's awareness."


That awareness now includes, like Washington, testing both suspicious-acting animals and also a larger sample of apparently healthy ones. In the past four years, Idaho has tested about 300 deer and elk for CWD, by the figuring of IFW Wildlife Veterinarian Mark Drew. Half of those have been tested in the past year.


"We're trying to get road kill from every region of the state," says Drew.


To date, officials have not found any Idaho deer or elk suffering from CWD. But like their counterparts in Washington, they say this slow, mysterious and troubling illness is something they must keep looking for. And hoping never to discover.


"This is a full-court press," says Mitchell. "It's not a major panic, but it's something that must have good professional attention from now on, unfortunately. If it ever did break out, it's the nuclear winter of wildlife."